In a niche website+adsense, what should be ideal global mont

[eook.joc]

Hi,
I have done quite a bit research on niche website and here are my findings:
1>For a niche website the keywords chosen should be of low competition and high cpc (This can be checked from google keyword tool)

2>Keeping website on Low competition keywords would help in reaching the 1st page of google ==> more traffic.

3>High cpc keywords will get more $ per click, obviously there is a trade off low competition keywords are generally of low cpc but there has to be a balance.

So my question is to have low competition keywords what should be ideal global monthly search? it is normally said to be 2000-3000 per month is it right?

can the global search count of keywords be ~500/month is it too low?

Any other tips for building a niche website?
"Rosetta Stone Arabic Rosetta Stone Japanese"